1. Field of the Invention
This invention relates to windshield wiper equipment and more particularly to an improved windshield wiper blade having a backing member for receiving and transmitting wiper arm pressure directly from the superstructure to the wiping element.
2. Description of the Prior Art
Traditionally, since the invention of John W. Anderson, U.S. Pat. No. 2,693,063, windshield wiper blades have been constructed with a superstructure operatively connected to a backing strip which, in turn, is operatively connected with a resilient wiping element. Various forms of superstructures have been used, all of which receive pressure from a windshield wiper arm and apply the pressure at two or more points to the backing strip. The pressure from the superstructure to the backing strip is applied through pairs of inwardly facing claws which embrace the outer edges of the backing strip so that pressure from the superstructure is applied through the claws to the edges of the backing strip and from there, on to the resilient wiping element. The claws on the superstructure are designed to move longitudinally with respect to the backing strip so as to permit the backing strip to conform to a surface being wiped.
More recently, the backing strips have been made of plastic which requires special shaping in order to provide the necessary stiffness parallel to the surface being wiped and sufficient flexibility as well as stiffness in a direction transverse to the surface being wiped in order to permit the pressure from the superstructure to be distributed substantially evenly along the length of the blade. The use of plastic for the backing strip generally has taken the form of a tubular portion open on one side substantially throughout its length. Outwardly extending flanges are formed on opposite sides of said tubular portion such that the claws of a superstructure are adapted to slidably engage the outer edge portions thereof. Applying pressure in a traditional way through the claws to the outer flanges of the plastic flexor has, in many instances, been less than completely satisfactory. That is, the plastic does not have sufficient stiffness to accept the pressure from the superstructure and transmit it over a substantial portion of the blade so that substantially equal pressure will be applied to the rubber wiping element. As a result, there is a tendency for blades with plastic flexors or backing strips to leave streaks on the surface being wiped due to the uneven distribution of pressure from the superstructure through the backing strip to the wiping element.